Metering apparatus for material divided into small particles



Dec. 15, 1959 A. H. NIMBLETT, JR 2,917,343

METERING APPARATUS FOR MATERIAL DIVIDED INTO SMALL PARTICLES Filed Feb. 20, 1956 3 Sheets-Sheet 1 INVENTO 4155/?7 h. N/MBLfT BYWMI ATTORNEY Dec. 15, 1959 A. H. NIMBLETT, JR

METERING APPARATUS FOR MATERIAL DIVIDED INTO SMALL PARTICLES 3 Sheets-Sheet 2 Filed Feb. 20, 1956 INVENTOR: ALBERT H NIMBLE 77, JK. BY W M ATTORNEY Dec. 15, 1959 A. H. NIMBLETT, JR 2,917,343

METERING APPARATUS FOR MATERIAL DIVIDED INTO SMALL PARTICLES Filed Feb. 2o, 1956 s Sheets-Sheet 3 IN VEN TOR: ALBL'RT H N/MBLETT; JR.

ATTORNEY United States Patent METERING APPARATUS FOR MATERIAL DIVIDED INTO SMALL PARTICLES Albert l-l. Nimblett, Jr., Salem, Mass., assignor, by mesne assignments, to Sylvania Electric Products Inc., Wilmington, Del., a corporation of Delaware Application February 20, 1956, Serial No. 566,540

3 Claims. (Cl. 30252) This invention relates generally to metering apparatus and more particularly to such apparatus adapted to feeding powdered material at a constant rate.

Apparatus according to my invention is especially useful for metering materials to be deposited on the surfaces of articles by an electrostatic field. Articles which may advantageously be coated in this manner include electric lamp bulbs such as the outer glass envelopes of mercury vapor lamps which may require color corrective or fluorescent coatings on their interior surfaces. For such applications, coating material or powder is dispensed into an air stream to form a so-called smoke or suspension of solid particles in air, which is thereafter conveyed into the electrostatic field by which the deposition is effected.

Several difiiculties are encountered in satisfactorily metering such materials because of the nature of the materials involved and the small quantities required. Typically, the coating of 1400 bulbs in an hour may require as little as pound. The coating materials are generally mechanical mixtures of different ingredients, each of a characteristic specific gravity and particle size range. Since the size of particles may vary from a fraction of a micron to a maximum of about forty microns, a quantity of such material in a reservoir, for example, has a tendency to arrange itself into a self-supporting structure of interlocked particles which will not flow, by gravity into a conveyor. Moreover, efforts to encourage the flow of powder by severe agitation, usually cause heavier particles and those of small size to settle to the bottom of the reservoir, thus continuously changing the proportion of ingredients in the delivered material. When these proportions have changed sufiiciently to be objectionable, it becomes necessary to halt the coating process for discarding material in the reservoir which must be replaced by fresh powder. Such replacement is costly in materials and in lost production time. On the other hand, if a compressive force is applied to the material to cause it to flow, adjacent particles tend to cohere, and to form undesirable specks in the coating. It is accordingly an object of my invention to increase the efiiciency of such coating processes by improving the metering of coating materials.

- Another object is to provide apparatus for metering such materials without separation of ingredients in the mixture or objectionable cohesion between initially separate particles.

An additional object is to provide such apparatus adapted to feeding powdered materials in small quantities.

These and other objects are achieved in an illustrative embodiment according to my invention by a novel arrangement of a conveyor and means for urging powdered material onto the conveyor. The powder is deposited into a suitable hopper in quantity sufificient to cover the conveyor which is driven continuously therethrough. The conveyor may conveniently be in the form of a flexible core around which a wire is helicallly wound, the wire defining a plurality of powder carrying spaces between its adjacent turns. The powder urging means includes a rotor member revolved continuously at a relatively slow speed and having fingers, on said rotor, which pass in close proximity to the conveyor at several points along the length of its path within the hopper. The fingers displace interlocked particles in the vicinity of the conveyor thus allowing the powder to flow into the spaces. The powder is carried out of the hopper by the conveyor from which it may be discharged by air under pressure which forms with the powder a smoke adapted to being electrostatically deposited upon the interior surfaces of bulbs.

The foregoing and other objects, advantages and novel features of my invention willbe clear from the following detailed description of an illustrative embodiment thereof taken in connection with the accompanying drawings in which:

Figure 1 is a'plan view of apparatus according to my invention;

Figure 2 is a view in side elevation and partially in cross section showing the apparatus of Fig. l;

Figure 3 is a fragmentary sectional view to an enlarged scale showing more clearly a novel powdered material conveyor which is a part of my apparatus.

Turning to the drawings, I will now describe my apparatus which includes a base plate 10 on which are mounted an electric motor 12, a variable speed reducer 14 and an auxiliary base plate 16. The plate 16 is supported on the base 10 by posts 18. A hopper indicated at 20 is formed of vertical panels 22 and a bottom 24. The hopper 20 is supported by brackets 26 on the plate 16 and by a longer bracket 28 on the base 10. Powder to be mixed with air to form smoke is supplied to the hopper 20 from which it is taken by an endless conveyor indicated at 30. The powder is loaded into the conveyor 30 by the action of fingers 32 depending from rotor body 34 which is rotated at a relatively slow speed by motor 36 through variable speed reducer 38. Shaft 42 integral with the body 34 is connected to shaft 40 of the speed reducer 38 by means of a sleeve 44. The motor 36 and the reducer 38 are supported on a bracket 46 fixed to cover 48 which closes the hopper 20.

The conveyor 30 which includes a core 50 of flexible material and a wire 52 helically wound about the core passes over an idler pulley 54 rotatable on a bracket 55 which is upstanding on the plate 16. The conveyor 30 enters the hopper 20 through a suitable opening in the wall 22 adjacent the pulley 54, travels through the hopper to a similar opening in the opposite wall 22 and exits through a conduit tube 56 which is joined as by welding to the panel 22 at the latter opening. The conveyor 30 also passes over a circumferentially V-notched drive sheave 58 and a tension adjusting sheave 60. The sheave 58 is mounted on drive shaft 62 of the speed reducer 14, whereas the sheave 60 is adjustable vertically on bracket 64 for regulating tension of the conveyor 30 by means of a slot (not shown) in the bracket which depends from the plate 16.

I The conveyor 30 passes through the tube 56 and venturi 66 formed in pipe 68 which connects the tube 56 with a second venturi tube 70. The venturi 66 is supplied through hose 72 with air under pressure from a source not shown. Hose 74 connects the venturi tube 70 with an electrostatic coating head indicated at 76. An additional hose 78 at the end of the tube 70 opposite the hose 74 is in communication with an arrangement of conventional valves not shown. Through these valves, the hose 78 may be closed off or in the alternative coupled 3. either to a supply of air under moderate pressure or to a high pressure air source.

The head 76 is rotatably mounted on a supporting plate, 8.0 and includes a set of upstanding fingers 82 for positioning a glass envelope or bulb 84 shown in phantom in- Fig. 2. The head 76 and the bulb 84 are rotated as a unit about nozzle 86 and ground electrode 88 by a suitably driven belt 90 which passes over a sheave 92. A high electrical potential is applied to the bulb 84 by means of a burner having an electrically conductive flame (not shown) contacting the exterior surface of the bulb which isinsulatedly supported and continuously rotated by the head 76 during the coating operation.

The operation of my apparatus Will now be described in detail with initial reference to Fig. 3. A sufiicient quantity of coating material or powder 94 is maintained in the hopper 20 to cover the conveyor 30 and a portion of the fingers 32. The conveyor 30 is drawn continuously through the powder 94 and the rotor 34 is revolved constantly at a relatively slow speed which does not unduly agitate the powder. The lower ends of the fingers 32 pass in close proximity to the conveyor 30 at several points along the portion of its path which lies within the hopper 20. The fingers at these points urge bodies 96 of powder into the spaces between adjacent turns of the wire 52. The bodies 96 are thereafter carried into the, tube 56 by the conveyor 30. The spacing between the fingers 32 and the conveyor 30 has been exaggerated in the drawings for purposes of clarity. In the tube 56, the. bodies 96 are carried in the spaces, formed by the wire 52 between the core 50 and the internal walls of the tube. Clearance between the conveyor 30 and the tube which is limited in practice to proportions adequate to assure a running fit has also been exaggerated for clarity.

Air introduced into the venturi 66 through the tube 72 removes the powder from the conveyor 30. The powder is carried in the form of smoke through the pipe 68, the venturi 70, and the hose 74 to the interior of the bulb, 84 on the head 76. At the head 76 the smoke enters the bulb 84 through the nozzle 86 and is thereafter deposited on the interior surface of the bulb by the force of the electrostatic field acting upon the particles.

The venturi 66 effectively isolates the hopper 20 from the air under pressure introduced through the hose 72 so that no agitation of the contents of the hopper occurs. The venturi tube 70.not only facilitates the cleaning of the hose 74 but also permits the dilution of smoke delivered thereto through the pipe 68. Particles which adhere to the interior walls of the hose 74 may thus be removed periodically by a blast of high pressure air from the hose 78 without agitating the contents of the hopper 20 or the need for closure of intermediate passages. Since smoke at the venturi tube 70 may be diluted by air added through the hose 78, the smoke-producing capacity of my apparatus may be greatly increased. When a limited volume of smoke is required, the hose 78 may be closed and smoke of suitable density for electrostatic deposition supplied to the venturi 70. But in. order to provide greater volume delivery, the speed of the conveyor 30 maybe increased to a point where smoke arriving at the venturi 70 is considerably denser than that which is suitable for the application. The dense smoke is diluted by air from the hose 78 thus providing a greatly expanded volume of smoke of suitable sas What I claim is:

1. Metering apparatus for powdered material, said apparatus comprising: walls forming a reservoir for a quantity of said material; an endless conveyor passing through opposite walls of said reservoir and the said material therein, said conveyor including a flexible core and a wire helically wound around said core and defining materialcarrying spaces between adjacent turns thereof; means for urg ng portions of said material into said spaces; means for driving said conveyor continuously for transporting the material priorly urged into said spaces to a discharge area outside said reservoir; and means in said area for removing said material from said spaces.

2. Metering apparatus for powdered material, said apparatus comprising: walls defining a reservoir for a quantity of said material; an endless conveyor passing through opposite walls of said reservoir and the said material therein, said conveyor including a flexible core and a wire wound helically around said core and defining materialcarrying spaces between adjacent turns thereof; a continuously revolving rotor in said reservoir; fingers mounted on said rotor each having a free end which passes adjacent said conveyor as said rotor revolves whereby por-. tions of said material are urged into said spaces; means for driving said conveyor continuously for transportingsaid material from said conveyor.

3. Metering apparatus for powdered material, said apparatus compr sing: walls forming a reservoir for a quantity of said material; an endless conveyor passing through opposite walls of said reservoir and the said material therein, said conveyor including a flexible core and a wire helically wound around said core and defining material-carrying spaces between adjacent turns thereof; a continuously revolving rotor in said reservoir; fingers mounted on said rotor, each having a free end which passes adjacent said conveyor as said rotor revolves whereby portions of said material are urged into said spaces; means for driving said conveyor continuously for transporting the material in said spaces to a discharge area outside said reservoir; and means in said area for directing a flow of air under pressure over said conveyor to discharge from said conveyor material priorly urged into said spaces.

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